This application claims the benefit of U.S. Provisional Application No. 60/547,217, filed Feb. 24, 2004.
Non-volatile storage is essential to virtually all computer systems, from notebooks to desktops to large data centers employing clusters of servers. Non-volatile storage serves as a secure data repository which prevents data loss in the event of an unexpected interruption in primary power. Some common forms of non-volatile storage are packaged as non-volatile storage modules (NVSM) that can employ a magnetic disk (under control of a magnetic disk drive), flash memory components, or even magnetic tape (under control of a magnetic tape drive) as the non-volatile storage medium for the module.
One of the downsides of non-volatile storage is that it is relatively slow to access compared to volatile forms of memory such as DRAM (Dynamic Random Access Memory). Thus, virtually all computer systems also include volatile memory (VM) in which to temporarily store data for faster access. Typically, code for executing application programs and data recently used by active applications are stored to and retrieved from the non-volatile storage and stored in the VM for faster access.
Recently, a hybrid form of storage has been developed that seeks to provide the persistence of non-volatile storage but an access speed comparable to VM. This form of storage is commonly known as a solid state disk (SSD). The SSD typically includes DRAM or some other form of VM and an NVSM that employs a non-volatile storage medium such as a magnetic disk, flash memory or the like. The SSD also typically includes a back-up or secondary power source such as a battery. The internal battery supply is used in the event that primary power is lost, with sufficient capacity to continue refreshing the VM while all of the data stored therein is saved off to the NVSM. Once primary power is restored, the data can be retrieved and stored back into the VM for access by the host computer system to which it is coupled.